A much needed new report “Reducing Air Pollution from Houston-Area School Buses,” explains the impact of school bus pollution and gives school districts, policy makers, and citizens the information necessary to reduce emissions that affect student health. In its study, the Galveston-Houston Association for Smog Prevention found that the 7,500 school buses in the Houston-Galveston area emit 6 tons of nitrogen oxide, 381 pounds of particulate matter, and 1,300 pounds of noxious volatile organic compounds each school day. The study found that NOx reduction technologies still have a way to go, but that technologies to reduce particulates are widely available, cost effective, and essential to improve student health.

A large amount of the air pollution from school buses in the Houston-Galveston area comes from older, dirtier buses. Because school buses are driven fewer miles than heavy-duty trucks, school districts hold on to older vehicles for much longer than other fleet owners. The GHASP study found that one-quarter of the school buses in the Houston-Galveston region were built before 1990 and that these buses release an average of six times more PM and almost three times more NOx than today’s average diesel bus. Purchasing retrofit technologies for pre-1990 buses is not usually cost effective because the buses are near the end of their lives. Instead, school districts should be replacing pre-1990 buses as quickly as possible.

Because serious NOx reductions will be necessary in the Houston-Galveston region to comply with the Clean Air Act, the federal government has made some limited funding available to help reduce NOx. School districts are eligible for this funding, but GHASP determined that available NOx-reduction technologies are still too expensive to qualify for available grants. Change, however, may be just around the corner. Some new selective catalytic reduction and exhaust gas re-circulation systems can reduce NOx by up to 90%, and these technologies are dropping in price.

Fortunately, school districts do not need to wait to reduce their harmful particulate emissions. High levels of PM pollution can pose a direct health risk to children, causing adverse respiratory effects, such as asthma, reduced lung function, and acute respiratory illness. A number of studies, too, have associated particulate pollution with cardiovascular disease and death. Children are especially susceptible to pollution-induced illnesses because they inhale 50% more air per pound of body weight.

While school buses are idling at schools, traffic lights, and bus stops, fine PM levels inside the buses rise dramatically, and students riding or standing near the bus may be put at risk. When students are being dropped off at school or boarding buses to go home, a large number of buses may be gathered in a small space. Many schools have driveway coverings that keep particulate matter from dispersing quickly, and both riders and drivers can be exposed to especially high concentrations of PM. This hazard is eliminated if drivers turn off their engines until it is time for buses to leave. The Houston Independent School District has a model program to ensure that buses do not idle during pick ups and drop offs, but nearly two-thirds of area school districts did not report a bus idling policy when GHASP was doing its research. It is hard to imagine an excuse for not taking this simple and cost-free measure to protect student health.

In addition to instituting and enforcing clear idling policies, districts need to retrofit as many buses as possible with cost-effective technologies that reduce PM pollution. Two main technologies have operated successfully on buses around the country.
• Diesel PM filters fit almost all buses built after 1990 and reduce PM by 85% and volatiles by at least 60%. The filters cost between $1,000 and $1,500 per bus.
• A less expensive alternative, offering a lower percentage reduction, is a diesel oxidation catalyst, which can fit older buses and reduce PM emissions by 20% and VOCs by over 40%, for about $500 per bus. With new diesel buses costing over $60,000 each, the relatively small expense of retrofitting a bus is easily justified.

In summary, the GHASP report has analyzed a number of aggressive scenarios for reducing all school bus emissions over time. While government and industry continue moving in the direction of reducing all school bus emissions, the community should use this report to make a concerted effort to reduce PM emissions now. School districts need to implement strong idling policies and retrofit as many post-1990 buses as they can afford with PM filters and diesel catalysts. When cash-strapped districts have done all they can, parents and teachers must urge the government to provide funds to speed this process and improve student health.